1. Field of the Invention
The present invention relates to sensor failure detection, and it particularly relates to sensor failure detection with improved swiftness, easiness etc.
2. Description of the Related Art
For example, various sensors are provided in an electronic control device of an automobile internal combustion engine, such as a diesel engine, and detection signals of the various sensors are used for operational control of the internal combustion engine.
One example of such a sensor is a pressure sensor that detects rail pressure in a common rail type fuel injection control apparatus. The pressure sensor is important to achieve appropriate fuel injection, and various types of methods have been proposed to detect a failure.
As one of failure diagnosis methods of the pressure sensor in the common rail type fuel injection control apparatus, for example, a method has been proposed in which, when a failure of the pressure sensor is diagnosed, a command to intentionally increase the rail pressure is performed, while a command to decrease an energization time of an injector is given. In this method, it is assumed that there is no failure with the pressure sensor when it is determined that there has been no change in a fuel injection amount and exhaust gas properties as a result of the commands as disclosed, for example, in JP-A-10-325352.
However, in the above-described failure diagnosis method, in order to detect the failure of the pressure sensor, it is necessary to issue the command to increase the rail pressure unnecessarily, irrespective of an actual fuel injection. This not only creates redundancy in a control operation, but also there is a risk that an unnecessary increase of the rail pressure may actually occur for some reason, which has an impact on a fuel injection operation.